Some microelectromechanical system (MEMS) devices are required to operate over wide temperature ranges, but the performance of these devices is often adversely affected by temperature changes. For example, the bias and scale factor of MEMS inertial sensors varies significantly from −45° C. to 85° C. To minimize these effects, sensor output data is often temperature-compensated based on a one-time factory calibration. Calibration mitigates errors but does not eliminate them entirely. One method often used to further improve a MEMS device is to keep the device heated at a temperature just above the maximum specified operating temperature. Stabilizing the MEMS device temperature theoretically eliminates the adverse effects of temperature change.
Temperature stabilization often requires unacceptable levels of power consumption. Active temperature control can be performed with limited power consumption if sufficient thermal isolation is achieved. Sufficient thermal isolation in prior art systems requires increasing the complexity (and thus the cost) because of the constraints imposed on device geometry and materials.
The solutions provided by the prior art include non-monolithic systems in which a thermal isolation stage is fabricated separately from the MEMS die. After fabrication of the thermal isolation stage, a MEMS die is attached to the thermal isolation stage by soldering, thermo-sonic bonding, bump bonding, etc. Cost and complexity is increased by the need for both: 1) a process to fabricate the separate thermal isolation stage; and 2) a process to attach the MEMS die to the thermal isolation stage. The additional processing to attach the die to the thermal isolation stage can be detrimental to long term stability of the MEMS die and lead to degraded performance due to mechanical drift of the attachment points.